This invention relates to an improved design for fuel assemblies for liquid metal fast breeder reactors (LMFBR).
One of the accidents for which an LMFBR plant must be analyzed is the Hypothetical Core Disruptive Accident (HCDA). This accident involves a grossly disrupted core in which a substantial amount of nuclear fuel and cladding has melted. The nuclear fuel of an LMFBR is normally cooled by an upward flow of liquid coolant, usually sodium, over the surface of the fuel rods. During an HCDA, it is considered possible that the movement of the molten cladding may form blockages which reduce the potential for permanent removal of fuel from the core region, i.e. bottling-up the core, and consequent permanent sub-criticality.
It is desired to provide a fuel assembly design which reduces or eliminates the potential for cladding or fuel freezing and consequent plugging or bottling-up of the core region.